OCULOMOTOR (III), TROCHLEAR (IV) AND ABDUCENS (VI) NERVES
A lesion of the III nerve produces impairment of eye and lid movement as well as disturbance of pupillary response.
Pupil: The pupil dilates and becomes 'fixed' to light.
Shine torch in affected eye - contralateral pupil constricts (its III nerve intact). Absent or impaired response in illuminated eye.
When light is shone into the normal eye, only the pupil on that side constricts.
Ptosis: Ptosis is present if the eyelid droops over the pupil when the eyes are fully open. Since the levator palpebrae muscle contains both skeletal and smooth muscle, ptosis signifies either a III nerve palsy or a sympathetic lesion and is more prominent with the former.
Steady the patient's head and ask him to follow an object held at arm's length. Observe the full range of horizontal and vertical eye movements.
Note any malalignment or limitation of range.
Examine eye movements in the six different directions of gaze representing maximal individual muscle strength.
Looking up and out superior rectus \
Looking up and in inferior oblique
Looking down and out inferior rectus
Looking down and in superior oblique
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